Graphics processing of a vertex buffer using a relative index buffer

ABSTRACT

Methods, apparatus and articles of manufacture for graphics processing of a vertex buffer using a relative index buffer are disclosed. Example methods to process a vertex buffer disclosed herein include accessing a first relative index stored in a relative index buffer, the first relative index specifying an offset from a current index selecting a first entry of the vertex buffer. Such disclosed example methods also include, in response to the first relative index being a nonzero value, processing data associated with a second entry of the vertex buffer to determine a rasterizer output associated with the first entry of the vertex buffer, the second entry of the vertex buffer being selected using the current index offset by the first relative index.

FIELD OF THE DISCLOSURE

This disclosure relates generally to graphics processing and, moreparticularly, to graphics processing of a vertex buffer using a relativeindex buffer.

BACKGROUND

In graphics processing, rasterization refers to an image renderingprocess in which an image described in a vector graphics format usingpolygons, such as triangles, is converted into a raster image containingpixels. For example, a rasterizer may process an input vertex buffercontaining vertex data specifying the vertices of the triangles makingup an input image to produce an output raster image capable of beingoutput on a video display, printed by a printer, saved to a storagemedium, etc. Rasterization may include, or may be preceded by, othergraphics processing operations, such as (1) performing one or moretransformation operations (e.g., translation, scaling, rotation, etc.)on the triangles represented by the vertices in the vertex buffer, (2)performing clipping to truncate the triangles to fit within a definedviewing area of the output image, (3) performing shading to adjust thevisual characteristics (e.g., color, brightness, texture, etc.) of thetriangles represented by the vertices in the vertex buffer, etc.

In at least some examples, rasterizers may process the input vertexbuffer using a walking counter (or similar mechanism) to access vertexbuffer entries (also referred to herein as vertex buffer elements)in-order for rasterization. Additionally or alternatively, rasterizersmay use a separate absolute index buffer storing a sequence of absolutevertex buffer indices for use in accessing different entries of thevertex buffer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a first example graphics rendering systemcapable of processing a vertex buffer using a relative index buffer asdisclosed herein.

FIG. 2 is a block diagram of a second example graphics rendering systemcapable of processing a vertex buffer using a relative index buffer asdisclosed herein.

FIG. 3 is a block diagram of an example vertex buffer fetcher forprocessing a vertex buffer using a relative index buffer in the examplegraphics rendering systems of FIGS. 1 and/or 2.

FIG. 4 illustrates an example operation of the vertex buffer fetcher ofFIG. 3 to access vertex buffer entries using a relative index buffer.

FIG. 5 is a flowchart representative of example machine readableinstructions that may be executed to implement the example graphicsrendering systems of FIGS. 1 and/or 2, and/or the example vertex bufferfetcher of FIG. 3.

FIG. 6 is a flowchart representative of example machine readableinstructions that may be used to implement the example machine readableinstructions of FIG. 5 and/or that may be executed to implement vertexbuffer redundancy checking in the example graphics rendering systems ofFIGS. 1 and/or 2, and/or the example vertex buffer fetcher of FIG. 3.

FIG. 7 is a flowchart representative of example machine readableinstructions that may be used to implement the example machine readableinstructions of FIG. 5 and/or that may be executed to implementhardware-based processing of a vertex buffer using a relative indexbuffer in the example graphics rendering systems of FIGS. 1 and/or 2,and/or the example vertex buffer fetcher of FIG. 3.

FIG. 8 is a flowchart representative of example machine readableinstructions that may be used to implement the example machine readableinstructions of FIG. 5 and/or that may be executed to implementsoftware-based processing of a vertex buffer using a relative indexbuffer in the example graphics rendering systems of FIGS. 1 and/or 2,and/or the example vertex buffer fetcher of FIG. 3.

FIG. 9 is a block diagram of an example processor platform that mayexecute the example machine readable instructions of FIGS. 5-7 and/or 8to implement the example graphics rendering systems of FIGS. 1 and/or 2,and/or the example vertex buffer fetcher of FIG. 3.

Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts, elements, etc.

DETAILED DESCRIPTION

Methods, apparatus, systems and articles of manufacture (e.g., physicalstorage media) to perform graphics processing of a vertex buffer using arelative index buffer are disclosed herein. Disclosed example methods toprocess a vertex buffer include accessing a first relative index storedin a relative index buffer. In such examples, the first relative indexspecifies an offset from a current index selecting a first entry of thevertex buffer. In response to the first relative index being a nonzerovalue, such disclosed example methods also include processing dataassociated with a second entry of the vertex buffer to determine arasterizes output associated with the first entry of the vertex buffer.In such examples, the second entry of the vertex buffer is selectedusing the current index offset by the first relative index.

Some disclosed example methods further include fetching and processingthe first entry of the vertex buffer to determine a rasterizer outputassociated with the first entry of the vertex buffer in response to thefirst relative index being zero.

In some disclosed example methods, the first relative index isassociated with the first entry of the vertex buffer, and the firstrelative index is selected from the relative index buffer using thecurrent index. Additionally or alternatively, in some such examplemethods, the relative index buffer stores relative indexes associatedwith respective entries of the vertex buffer. Furthermore, in some suchexamples, the relative index buffer is accessed iteratively using thecurrent index, and the current index is incremented at each iteration ofaccessing the relative index buffer.

In some disclosed example methods, the data associated with the secondentry of the vertex buffer is cached data associated with the secondentry of the vertex buffer. Additionally, in some such example methods,processing the data associated with the second entry of the vertexbuffer can include calculating an index value corresponding to thecurrent index offset by the first relative index, and calling arasterizer using the index value. In some such examples, calling therasterizer using the index value causes the hardware rasterizer toaccess the cached data associated with the second entry of the vertexbuffer.

In some disclosed example methods, processing the data associated withthe second entry of the vertex buffer can include accessing first datafrom a vertex cache when the vertex cache is present. In such examples,the first data was obtained from previous rasterization processingassociated with the second entry of the vertex buffer and stored in thevertex cache. However, when the vertex cache is not present, suchexample methods can also include fetching second data included in thesecond entry of the vertex buffer, and performing rasterization usingthe fetched second data.

Some disclosed example methods further include comparing entries of thevertex buffer with past entries of the vertex buffer within a priornumber of vertex buffer entries. For example, the prior number ofentries can be based on a relative index size. In response todetermining that the first entry of the vertex buffer matches the secondentry of the vertex buffer, such example methods also include, settingthe first relative index equal to an offset between the first entry ofthe vertex buffer and the second entry of the vertex buffer.

These and other example methods, apparatus, systems and articles ofmanufacture (e.g., physical storage media, such as storage devicesand/or storage disks) to perform rasterization of a vertex buffer usinga relative index buffer are disclosed in greater detail below.

As noted above, in at least some examples, rasterizers used for graphicsprocessing may be configured to access entries of a vertex buffer usingan absolute index buffer storing a sequence of absolute vertex bufferindices pointing to specific entries of the vertex buffer. Under such aconfiguration, a rasterizer can retrieve the absolute indices from theabsolute index buffer sequentially (e.g., iteratively), and then accessthe respective vertex buffer entries indexed by the retrieved absoluteindices. The use of such an absolute index buffer can allow entries ofthe vertex buffer to be re-used and/or accessed out-of-order,potentially enabling the total number of vertex buffer entries to bereduced. However, there are several potential drawbacks with using anabsolute index buffer to process a vertex buffer. For example, use of anabsolute index buffer to access entries of the vertex buffer may alsoincur additional processing overhead (e.g., associated with creating theabsolute index buffer and retrieving the absolute vertex buffer indicesfrom the absolute index buffer) relative to use of a walking counter toaccess entries of the vertex buffer in-order. Also, absolute indexbuffers are not usually compressible, and the size of the absoluteindices can be large and also can place an arbitrary bound on the numberof vertices capable of being addressed. Additionally, absolute indexbuffers may not be able to readily account for mutation of the vertexdata.

As further noted above, in at least some examples, rasterizers used forgraphics processing may additionally or alternatively be configured touse a walking counter or similar mechanism to iteratively access vertexbuffer entries in-order (e.g., sequentially). Under such aconfiguration, a rasterizer may incur less processing overhead than arasterizer configured to use absolute index buffers to access theentries of the vertex buffer. However, rasterizers configured to accessthe vertex buffer entries in-order may also suffer from potentialdrawbacks. For example, because the vertex buffer entries are accessedsequentially, such rasterizers are unable to take advantage ofredundancies in the vertex data included in the vertex buffer.Accordingly, rasterizers configured to access the vertex buffer entriesin-order may waste processing power to rasterize duplicate vertex datain the vertex buffer.

Graphics processing of vertex buffers using relative index buffers, asdisclosed herein, can overcome at least some of the foregoingdeficiencies (and/or other deficiencies) of prior techniques. Asdescribed in greater detail below, a relative index buffer associatedwith a vertex buffer stores a sequence of relative indices correspondingto respective entries of the vertex buffer. For a given vertex bufferentry, the corresponding relative index in the relative index bufferspecifies an offset (e.g., such as a number of vertex buffer entries)from the given vertex buffer entry to a matching prior vertex bufferentry. In this way, the relative index buffer stores information (e.g.,the relative indices) describing the redundancy in its associated vertexbuffer. Accordingly, unlike prior techniques that access vertex bufferentries in-order, the disclosed graphics processing techniques are ableto use the disclosed relative index buffers to exploit redundancy in thevertex data contained in vertex buffers. Additionally, compared with theabsolute index buffers used in other prior techniques, the disclosedrelative index buffers contain relative indices that can besubstantially smaller than the absolute indices contained in theabsolute index buffers. Furthermore, unlike the prior absolute indexbuffers, the disclosed relative index buffers do not place an arbitrarybound on the number of vertices capable of being addressed, are amenableto compression, can be readily used with mutating data, and can be tunedto the characteristics of an output vertex cache included in thegraphics processing pipeline. These and other potential benefits ofusing relative index buffers for graphics processing of vertex buffers,as disclosed herein, will become apparent through the followingdisclosure.

Turning to the figures, a first example graphics rendering system 100capable of performing graphics processing of a vertex buffer using arelative index buffer as disclosed herein is illustrated in FIG. 1. Thefirst example graphics rendering system 100 includes an examplehardware-based graphics processor 105, also referred to as a graphicsprocessing unit (GPU) 105, to perform hardware-based rendering of inputvertex buffers to generate output raster images. As described above, avertex buffer, such as the example vertex buffer 305 illustrated in FIG.3 and described in greater detail below, contains a sequence of vertexdata specifying the vertices of triangles making up an input imagedescribed in a vector graphics format. The vertex data for a givenvertex stored in the vertex buffer can include, but is not limited to,location data (e.g., specifying the location of the vertex in two orthree dimensions), color data, texture data, etc. For example, the firstentry of the vertex buffer may contain the vertex data for a firstvertex of a triangle making up an image to be rendered, the second entryof the vertex buffer may contain the vertex data for a second vertex ofthe image, the third entry of the vertex buffer may contain the vertexdata for a third vertex of the image, etc. A further exampleimplementation of the vertex buffer 305 of FIG. 3 is illustrated in FIG.4, which is described in greater detail below.

The GPU 105 of the illustrated example can be implemented by any type ofGPU technology, such as any of the family of Intel® graphic mediaaccelerators (GMAs), any of the family of Advanced Micro Devices (AMD)®GPUs, any of the family of NVIDIA® GPUs, etc. For example, the GPU 105of FIG. 1 includes an example hardware (H/W) rasterizer 110implementing, in any appropriate manner, one or more rasterizationoperations to be performed on input vertex data to generate the pixeldata representing the output raster image. The GPU 105 of theillustrated example also include an example vertex transformer 112 toperform one or more pre-processing operations on vertex data prior tothe vertex data being processed by the H/W rasterizer 110. Examples ofsuch pre-processing operations that may be implemented by the vertextransformer 112 include, but are not limited to, (1) one or moretransformation operations, such as a translation operation, a scalingoperation, a rotation operation, etc., to be performed on the trianglesrepresented by the vertices in the input vertex buffer, (2) a clippingoperation to truncate the triangles represented by the vertices in theinput vertex buffer to fit within a defined viewing area of the outputimage, (3) a shading operation to adjust the visual characteristics(e.g., color, brightness, texture, etc.) of the triangles represented bythe vertices in the input vertex buffer, etc. The vertex data output bythe vertex transformer 112 for processing by the H/W rasterizer 110 isalso referred to herein as transformed vertex data. In the illustratedexample, the GPU 105 also include one or more example vertex caches 115to store the transformed vertex data generated by the pre-processingoperation(s) implemented by the vertex transformer 112 prior torendering of the vertex data by the H/W rasterizer 110 into the pixelsforming the output raster image. The vertex cache(s) 115 may beimplemented by any type(s) and/or number of caches, memories, storagedevices, etc.

In the illustrated example of FIG. 1, the GPU 105 is controlled by anexample video driver 120, which may be implemented, for example, inhardware, software, or any combination thereof. The video driver 120 ofthe illustrated example obtains an input vertex buffer, such as theexample vertex buffer 305 of FIG. 3, for rendering from one or moreapplications, such as an example application 125, capable of generatingimage and/or video data to be displayed or otherwise output by an outputdevice. For example, the application 125 can correspond to a video game,a media player, a word and/or other data processing program, a webbrowser, etc.

After obtaining the input vertex buffer from the application 125, theexample video driver 120 of FIG. 1 selects entries of the vertex bufferfor rendering. In the illustrated example, the video driver 120 includesan example vertex buffer fetcher 130 to select the entries of the vertexbuffer using a relative index buffer, such as the example relative indexbuffer 315 illustrated in FIG. 3 and described in greater detail below,in accordance with the examples disclosed herein. As described above andin greater detail below, the relative index buffer associated with theparticular input vertex buffer stores a sequence of relative indicescorresponding to respective entries of the vertex buffer. For a givenvertex buffer entry, the corresponding relative index in the relativeindex buffer specifies an offset (e.g., such as a number of vertexbuffer entries) from the given vertex buffer entry to a matching priorvertex buffer entry. A further example implementation of the relativeindex buffer 315 of FIG. 3 is illustrated in FIG. 4, which is describedin greater detail below.

In the illustrated example of FIG. 1, the vertex buffer fetcher 130iteratively accesses, in-order, successive entries of the relative indexbuffer for the input vertex buffer to determine a relative indexcorresponding to a next entry of the vertex buffer to be fetched andrendered. As described in greater detail below, during a given iterationin which a current vertex buffer entry is to be fetched and rendered,the respective relative index retrieved from the relative index bufferfor that iteration specifies an offset between the current vertex bufferentry and a prior matching vertex buffer entry, if one exists (e.g.,within the offset addressable by the relative indices). For example, ifthe relative index retrieved during a given iteration is equal to zero(0), then there are no prior vertex entries (e.g., within the offsetaddressable by the relative indices) that match the current vertexbuffer entry corresponding to the retrieved relative index. However, ifthe relative index retrieved during a given iteration is a non-zerovalue, then the current vertex buffer entry corresponding to theretrieved relative index has a matching prior vertex buffer entrylocated at an offset from the current entry in the vertex buffer equalto the value of the retrieved relative index.

In the illustrated example of FIG. 1, to cause the GPU 105 to render agiven entry of the vertex buffer, the vertex buffer fetcher 130 passes apointer to the start of the vertex buffer and a vertex buffer indexidentifying the vertex buffer entry to be rendered to the GPU 105. Asdescribed in greater detail below, during a given iteration in which acurrent vertex buffer entry is to be fetched and rendered, the vertexbuffer fetcher 130 of the illustrated example determines the vertexbuffer index identifying the actual vertex buffer entry to be fetchedand rendered to be a current iteration index (e.g., corresponding to thecurrent relative index buffer entry and the corresponding current vertexbuffer entry being processed) offset by the value of the relative indexlocated at the current iteration index in the relative index buffer. Forexample, if the relative index for a current iteration is a nonzerovalue, then there is a prior vertex buffer entry that matches thecurrent vertex buffer entry and the vertex buffer index, which is set tothe current iteration index offset by the relative index, points to thatmatching prior vertex buffer entry. In this example, when the GPU 105receives, from the vertex buffer fetcher 130, the vertex buffer index tobe used to fetch and render the current vertex buffer entry for thecurrent processing iteration, the vertex buffer index actually points tothe matching prior vertex buffer entry. Because the GPU 105 has alreadyprocessed that prior vertex buffer entry, the GPU 105 may detect thatthere is cached, transformed vertex data for that prior vertex bufferentry available in the vertex cache 115. Thus, the GPU 105 may be ableto fetch the cached vertex data for the prior vertex entry from thecache 115, instead of wasting resources to fetch and perform one or moreintermediate operations (e.g., using the vertex transformer 112) on thecurrent entry from the vertex buffer.

However, if the relative index for a current iteration is zero, thenthere is no prior vertex buffer entry matching the current vertex bufferentry and the vertex buffer index, therefore, equals the currentiteration index. In such an example, when the GPU 105 receives, from thevertex buffer fetcher 130, the vertex buffer index to be used to fetchand render the current vertex buffer entry for the current processingiteration, the vertex buffer index points to the current vertex bufferentry. Because the GPU 105 has not yet processed the current vertexbuffer entry (or has not processed a similar entry within a past numberof iterations able to be stored in the vertex cache 115), the GPU 105may detect that there is no cached vertex data for that current vertexbuffer entry. Thus, the GPU 105 may fetch the vertex data for thecurrent vertex entry from the vertex buffer and process the fetchedvertex data with, for example, the vertex transformer 112 and the H/Wrasterizer 110.

Accordingly, in some examples, the size (e.g., in terms of number ofbits, such as 4 bits, 8 bits, 16 bits, etc.) of the relative indicesstored in the relative index buffer may be tailored to correspond to thesize of the vertex cache(s) 115 included in the GPU 105. For example,the size of the relative indices stored in the relative index buffer maybe specified such that the maximum offset capable of being representedby a relative index is equal to, or otherwise is based on, the depth ofthe vertex cache(s) 115 (or, in other words, the number of vertexentries capable of being stored in the vertex cache(s) 115). Forexample, if a vertex cache 115 has a depth of 256 entries and, thus, cancache 256 vertices, the relative indices in the relative index buffermay be specified to have a size of 8 bits, because 2⁸=256.

As described in greater detail below, in some examples, the vertexbuffer fetcher 130 performs a redundancy checking procedure to generatethe respective relative index buffer to be associated with an inputvertex buffer when the vertex buffer is initially obtained by the videodriver 120. After determining the relative index buffer for the vertexbuffer, the vertex buffer fetcher 130 can further store the relativeindex buffer and its association with the vertex buffer for futurerendering of this same vertex buffer (e.g., to avoid having toregenerate the relative index buffer in the future). For example, thevertex buffer fetcher 130 can generate identification information (e.g.,via a hash function and/or other technique) for the vertex buffer andits relative index buffer, and use this identification information tolink the relative index buffer with the vertex buffer.

A second example graphics rendering system 200 capable of performingrasterization of a vertex buffer using a relative index buffer asdisclosed herein is illustrated in FIG. 2. The second example graphicsrendering system 200 performs uses an example software graphicsprocessor 205 to perform software-based rendering of input vertexbuffers to generate output raster images. Accordingly, the softwaregraphics processor 205 in the graphics rendering system 200 of theillustrated example includes an example software (S/W) rasterizer 210implementing, in any appropriate manner, one or more rasterizationoperations to be performed on input vertex data to generate the pixeldata representing the output raster image. Similar to the vertextransformer 112 of FIG. 1, the graphics processor 205 of the illustratedexample also include an example vertex transformer 212 to perform one ormore pre-processing operations on vertex data prior to the vertex databeing processed by the S/W rasterizer 210. Examples of thepre-processing operations that may be implemented by the vertextransformer 212 include, but are not limited to, one or moretransformation operations, a clipping operation, a shading operation,etc. The S/W rasterizer 210 and/or the vertex transformer 212 may beimplemented by instructions executed by any type of processor platform,such as the example processor platform 900 illustrated in FIG. 9 anddescribed in greater detail below. Also, similar to the vertex cache(s)115 included in the example system 100 of FIG. 1, the example graphicsrendering system 200 may include one or more example vertex caches 215to store the transformed vertex data generated by the pre-processingoperation(s) implemented by vertex transformer 212 prior to rendering ofthe vertex data by the S/W rasterizer 210 into the pixels forming theoutput raster image. The vertex cache(s) 215 may be implemented by anytype(s) and/or number of caches, memories, storage devices, etc.

In the illustrated example of FIG. 2, the graphics processor 205 isinvoked by an example video driver 220, which may be implemented, forexample, in hardware, software, or any combination thereof. Similar tothe video driver 120 of FIG. 1, the example video driver 220 of FIG. 2obtains an input vertex buffer, such as the example vertex buffer 305 ofFIG. 3, for rendering from one or more applications, such as the exampleapplication 125, capable of generating image and/or video data to bedisplayed or otherwise output by an output device. The video driver 220of the illustrated example also includes an example vertex bufferfetcher 230 to select entries of the vertex buffer for rendering using arelative index buffer, such as the example relative index buffer 315illustrated in FIG. 3, in accordance with the examples disclosed herein.Operation of the vertex buffer fetcher 230 is similar to operation ofthe vertex buffer fetcher 130 described above. For example, like thevertex buffer fetcher 130, the example vertex buffer fetcher 230 of FIG.2 iteratively accesses, in-order, successive entries of the relativeindex buffer for the input vertex buffer to determine a relative indexcorresponding to a next entry of the vertex buffer to be fetched andrendered. As noted above, for a given iteration in which a currentvertex buffer entry is to be fetched and rendered, the respectiverelative index retrieved from the relative index buffer for thatiteration specifies an offset between the current vertex buffer entrycorresponding to the retrieved relative index and a prior matchingvertex buffer entry, if one exists (e.g., within the offset addressableby the relative indices). Accordingly, like the vertex buffer fetcher130, during a given iteration in which a current vertex buffer entry isto be fetched and rendered, the example vertex buffer fetcher 230 ofFIG. 2 determines the vertex buffer index identifying the actual vertexbuffer entry to be fetched and rendered to be a current iteration index(e.g., corresponding to the current relative index buffer entry and thecorresponding current vertex buffer entry being processed) offset by thevalue of the relative index located at the current iteration index inthe relative index buffer.

However, in the illustrated example of FIG. 2, the vertex buffer fetcher230 invokes the graphics processor 205 to rasterize a current vertexbuffer entry as follows. If the vertex cache 215 is not present (e.g.,because prior transformed vertex data is not saved to be reused forprocessing future vertex buffer entries), or the relative index for thecurrent iteration is zero (0), then the vertex buffer fetcher 230fetches the vertex data from the vertex buffer entry indexed (or pointedto) by the determined vertex buffer index (which is equal to the currentiteration index offset by the value of the relative index in the currentrelative index buffer entry) and provides the fetched vertex data to thevertex transformer 212 and the S/W rasterizer 210 for rendering.However, if the vertex cache 215 is present, and if the relative indexfor a current iteration is a nonzero value, then there may be cached,transformed vertex data already stored in the vertex cache 215 for thematching prior vertex buffer entry identified by the vertex bufferindex. Accordingly, the vertex buffer fetcher 230 uses the vertex bufferindex (which is equal to the current iteration index offset by the valueof the relative index in the current relative index buffer entry) toaccess the vertex cache 215 and retrieve the cached vertex data obtainedfrom prior processing of the prior vertex buffer entry matching thecurrent vertex buffer entry by the vertex transformer 212. The vertexbuffer fetcher 230 can then provide this cached vertex data to the S/Wrasterizer 210 for further rendering. In this way, the vertex bufferfetcher 230 can avoid having the vertex transformer 212 waste resourcesto fetch and perform one or more intermediate operations on the vertexdata in the current vertex buffer entry, which is a duplicate of thematching prior vertex buffer entry.

Accordingly, in some examples, the size (e.g., in terms of number ofbits, such as 4 bits, 8 bits, 16 bits, etc.) of the relative indicesstored in the relative index buffer may be tailored to correspond to thesize of the vertex cache(s) 215 included in the system 200. For example,the size of the relative indices stored in the relative index buffer maybe specified such that the maximum offset capable of being representedby a relative index is equal to, or otherwise is based on, the depth ofthe vertex cache(s) 215 (or, in other words, the number of vertexentries, e.g., 16, 256, 65536, etc., capable of being stored in thevertex cache(s) 215). Also, similar to the vertex buffer fetcher 130 ofFIG. 1, in some examples, the vertex buffer fetcher 230 performs aredundancy checking procedure to generate the respective relative indexbuffer to be associated with an input vertex buffer when the vertexbuffer is initially obtained by the video driver 220. After determiningthe relative index buffer for the vertex buffer, the vertex bufferfetcher 230 can further store the relative index buffer and itsassociation with the vertex buffer for future rendering of this samevertex buffer (e.g., to avoid having to regenerate the relative indexbuffer in the future), as described above.

A block diagram of an example vertex buffer fetcher 300 that may be usedto implement the vertex buffer fetcher 130 of FIG. 1 and/or the vertexbuffer fetcher 230 of FIG. 2 is illustrated in FIG. 3. The vertex bufferfetcher 300 of the illustrated example accepts an example vertex buffer305 having entries storing a sequence of vertex data to be rendered. Thevertex buffer fetcher 300 includes an example redundancy checker 310 todetermine an example relative index buffer 315 to be associated with thevertex buffer 305. For example, the redundancy checker 310 can generatethe relative index buffer 315 for the vertex buffer 305 as follows.Assuming the relative indices stored in the relative index buffer 315are n=log₂ N bits in length, then the redundancy checker 310 readsentries of the vertex buffer 305 sequentially in-order and maintains aring buffer of the last N entries read from the vertex buffer 305. For acurrent entry read from the vertex buffer 305, the redundancy checker310 writes the current vertex buffer entry to the ring. The redundancychecker 310 also searches the ring backwards (or forwards with an offsetof 1) and sets the relative index for the current vertex buffer entry tobe the index of the first matching entry in the ring (e.g., modulo N).If there is no matching entry in the ring, then the redundancy checker310 sets the relative index for the current vertex buffer entry to beequal to zero (e.g., if the relative index was not already initializedto be zero beforehand). Accordingly, a relative index having a size ofn=log₂ N can specify an offset from 0 to −(N−1). For example, if n=8,then the relative index can specify an offset from 0 to −255 entries inthe vertex buffer 305.

In some examples, the length of the relative indices stored in therelative index buffer 315 is set based on the depth of the vertexcache(s) 115 and/or 215. For example, if a vertex cache has depth of Nentries, setting the size of the relative indices included in therelative index buffer 315 to be n=log₂ N enables the relative indices toindex any entry stored in the cache.

In some examples, the redundancy checker 310 can update the relativeindex buffer 315 to reflect changes in one or more subranges of thevertex buffer 305 by, for example, resetting the respective relativeindices in the relative index buffer 315 corresponding to the changedsubrange(s) of the vertex buffer 305 to be equal to 0. The zeroedrelative indices then cause those changed vertex buffer entries to befetched from the vertex buffer 305.

The illustrated example vertex buffer fetcher 300 of FIG. 3 operates tocause entries of the vertex buffer 305 to be rendered in-order (e.g.,sequentially) starting with a first entry in the buffer. Accordingly,the vertex buffer fetcher 300 includes an example walking counter 320 toincrement a current iteration index tracking each successive iterationof selecting a next vertex buffer entry for processing. In other words,the current iteration index identifies the current vertex buffer entryto be rendered, as well as the current relative index buffer entrycorresponding to this current vertex buffer entry. Accordingly, thecurrent iteration index is also referred to herein as a current indexselecting the current entry of the vertex buffer 305 to be rendered.However, the actual vertex buffer entry to be rendered during thecurrent iteration may be different from the current vertex buffer entryselected by the current iteration index due to the relative index valuespecified for the current vertex buffer entry. The walking counter 320can be implemented by any type of digital counter, counting logic, etc.,capable of producing an output that counts from an initial value (e.g.,0 or 1, etc.) up to a total number of entries in the vertex buffer 305(e.g., N−1 or N, where N is the total number of entries in the vertexbuffer 305).

For example, the vertex buffer fetcher 300 includes an example relativeindex retriever 325 to retrieve a current entry of the relative indexbuffer 315 corresponding to the current iteration index maintained bythe walking counter 320. The vertex buffer fetcher 300 further includesan example vertex buffer indexer 330 to determine a vertex buffer indexbased on the current iteration index maintained by the walking counter320 offset by the relative index retrieved by the relative indexretriever 325. For example, if the relative indices in the relativeindex buffer 315 specify negative offset values, then the vertex bufferindexer 330 can determine the vertex buffer index for the currentiteration by adding the relative index retrieved by the relative indexretriever 325 to the current iteration index maintained by the walkingcounter 320. However, if the relative indices in the relative indexbuffer 315 specify positive offset values, then the vertex bufferindexer 330 can determine the vertex buffer index for the currentiteration by subtracting the relative index retrieved by the relativeindex retriever 325 from the current iteration index maintained by thewalking counter 320. The vertex buffer index determined by the vertexbuffer indexer 330 of the illustrated example specifies the actualvertex buffer entry to be rendered for the current iteration, which maybe the same or different from the current vertex buffer entry specifiedby the current iteration index depending on the value of the relativeindex buffer entry corresponding to the current vertex buffer entry.

An example operation 400 of the relative index retriever 325 and thevertex buffer indexer 330 to further illustrate determination of avertex buffer index from a current iteration index and a relative indexis shown in FIG. 4. The example of FIG. 4 depicts an exampleimplementation of the vertex buffer 305 having six (6) entries indexedfrom 0 to 5 and containing respective vertex data to be rendered. Theexample of FIG. 4 also depicts an example implementation of the relativeindex buffer 315 having six (6) entries containing the relative indices(denoted as R_IDX(i) in FIG. 4) corresponding to the respective vertexbuffer entries (denoted as VERTEX_DATA(i) in FIG. 4) of the vertexbuffer 305.

In the example operation 400 of FIG. 4, the walking counter 320increments an example current iteration index 405 to select eachsuccessive entry of the vertex buffer 305 for rendering. At the firstiteration, the current iteration index 405 equals 0 and the relativeindex retriever 325 retrieves the first entry, R_IDX(0), from therelative index buffer 315. In the illustrated example, the value of theretrieved relative index is R_IDX(0)=0. Accordingly, the vertex bufferindexer 330 determines the vertex buffer index to be equal to the valueof the current iteration index 405 and, thus, the vertex buffer index(represented by the line 410) points to the first entry, VERTEX_DATA(0),of the vertex buffer 305. In other words, the value of 0 for therelative index R_IDX(0) represents an index miss for the first entry,VERTEX_DATA(0), of the vertex buffer 305, thereby indicating that thisentry of the vertex buffer 305 is to be fetched for processing.

At the second iteration of the illustrated example, the currentiteration index 405 is incremented by the walking counter 320 to beequal to 1 and the relative index retriever 325 retrieves the secondentry, R_IDX(1), from the relative index buffer 315. In the illustratedexample, the value of the retrieved relative index is R_IDX(1)=0.Accordingly, the vertex buffer indexer 330 determines the vertex bufferindex to be equal to the value of the current iteration index 405 and,thus, the vertex buffer index (represented by the line 415) points tothe second entry, VERTEX_DATA(1), of the vertex buffer 305. In otherwords, the value of 0 for the relative index R_IDX(1) represents anotherindex miss for the second entry, VERTEX_DATA(1), of the vertex buffer305, thereby indicating that this entry of the vertex buffer 305 is tobe fetched for processing.

At the third iteration of the illustrated example, the current iterationindex 405 is incremented by the walking counter 320 to be equal to 2 andthe relative index retriever 325 retrieves the third entry, R_IDX(2),from the relative index buffer 315. In the illustrated example, thevalue of the retrieved relative index is R_IDX(2)=0. Accordingly, thevertex buffer indexer 330 determines the vertex buffer index to be equalto the value of the current iteration index 405 and, thus, the vertexbuffer index (represented by the line 420) points to the third entry,VERTEX_DATA(2), of the vertex buffer 305. In other words, the value of 0for the relative index R_IDX(2) represents another index miss for thethird entry, VERTEX_DATA(2), of the vertex buffer 305, therebyindicating that this entry of the vertex buffer 305 is to be fetched forprocessing.

At the fourth iteration of the illustrated example, the currentiteration index 405 is incremented by the walking counter 320 to beequal to 3 and the relative index retriever 325 retrieves the fourthentry, R_IDX(3), from the relative index buffer 315. In the illustratedexample, the value of the retrieved relative index is R_IDX(3)=−1.Accordingly, the vertex buffer indexer 330 determines the vertex bufferindex to be equal to the value of the current iteration index 405 offsetby the value −1 and, thus, the vertex buffer index (represented by theline 425) points to the third entry, VERTEX_DATA(2), of the vertexbuffer 305. In other words, the non-zero value of −1 for the relativeindex R_IDX(3) represents an index hit for the fourth entry,VERTEX_DATA(3), of the vertex buffer 305, and the cached vertex datacorresponding to the third entry, VERTEX_DATA(2), can be used forrendering during the current iteration rather than fetching andprocessing the vertex data for the fourth entry, VERTEX_DATA(3).

At the fifth iteration of the illustrated example, the current iterationindex 405 is incremented by the walking counter 320 to be equal to 4 andthe relative index retriever 325 retrieves the fifth entry, R_IDX(4),from the relative index buffer 315. In the illustrated example, thevalue of the retrieved relative index is R_IDX(3)=−3. Accordingly, thevertex buffer indexer 330 determines the vertex buffer index to be equalto the value of the current iteration index 405 offset by the value −3and, thus, the vertex buffer index (represented by the line 430) pointsto the second entry, VERTEX_DATA(1), of the vertex buffer 305. In otherwords, the non-zero value of −3 for the relative index R_IDX(4)represents an index hit for the fifth entry, VERTEX_DATA(4), of thevertex buffer 305, and the cached vertex data corresponding to thesecond entry, VERTEX_DATA(1), can be used for rendering during thecurrent iteration rather than fetching and processing the vertex datafor the fifth entry, VERTEX_DATA(4).

At the sixth iteration of the illustrated example, the current iterationindex 405 is incremented by the walking counter 320 to be equal to 5 andthe relative index retriever 325 retrieves the sixth entry, R_IDX(5),from the relative index buffer 315. In the illustrated example, thevalue of the retrieved relative index is R_IDX(5)=0. Accordingly, thevertex buffer indexer 330 determines the vertex buffer index to be equalto the value of the current iteration index 405 and, thus, the vertexbuffer index (represented by the line 435) points to the sixth entry,VERTEX_DATA(5), of the vertex buffer 305. In other words, the value of 0for the relative index R_IDX(5) represents an index miss for the sixthentry, VERTEX_DATA(5), of the vertex buffer 305, thereby indicating thatthis entry of the vertex buffer 305 is to be fetched for processing.

Returning to FIG. 3, the illustrated example vertex buffer fetcher 300further includes an example graphics processor invoker 335 to invoke agraphics processor (e.g., such as the example GPU 110 of FIG. 1 and/orthe example graphics processor 210 of FIG. 2) to process the entry ofthe vertex buffer 305 indexed by the vertex buffer index determined bythe vertex buffer indexer 330. For example, the graphics processorinvoker 335 can be configured to invoke the GPU 105 of FIG. 1 bypassing, to the GPU 105, a starting index of the vertex buffer 305 andthe vertex buffer index determined by the vertex buffer indexer 330. Insome examples, the H/W rasterizer 110 then retrieves cached, transformedvertex data from the vertex cache(s) 115 or the vertex transformer 112fetches and processes vertex data from the vertex buffer 305 dependingon whether the vertex buffer index points to a prior entry or a currententry, respectively, of the vertex buffer 305.

Additionally or alternatively, the graphics processor invoker 335 can beconfigured to invoke the S/W graphics processor 205 by fetching vertexdata from the entry of the vertex buffer 305 indexed by the vertexbuffer index and providing the fetched vertex data to the S/W graphicsprocessor 205 when, for example, the vertex cache 215 is not present orthe vertex buffer index points to the current entry of the vertex buffer305. However, if the vertex cache 215 is present, and the vertex bufferindex points to the a prior entry of the vertex buffer 305, then thegraphics processor invoker 335 can retrieve cached, transformed vertexdata corresponding to the prior vertex buffer entry selected by thevertex buffer index and provide the cached vertex data to the S/Wrasterizer 210 create the corresponding rasterized data.

While example manners of implementing the systems 100 and/or 200 havebeen illustrated in FIGS. 1-4, one or more of the elements, processesand/or devices illustrated in FIGS. 1-4 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example vertex buffer fetchers 130, 230 and 300, theexample GPU 105, the example H/W rasterizer 110, the example vertextransformer 112, the example vertex cache 115, the example video driver120, the example application 125, the example S/W rasterizer 210, theexample vertex transformer 212, the example vertex cache 215, theexample video driver 220, the example vertex buffer 305, the exampleredundancy checker 310, the example relative index buffer 315, theexample walking counter 320, the example relative index retriever 325,the example vertex buffer indexer 330, the example graphics processorinvoker 335 and/or the example systems 100 and/or 200 of FIGS. 1-4 maybe implemented by hardware, software, firmware and/or any combination ofhardware, software and/or firmware. Thus, for example, any of theexample systems 100 and/or 200, the example vertex buffer fetchers 130,230 and/or 300, the example GPU 105, the example H/W rasterizer 110, theexample vertex transformer 112, the example vertex cache 115, theexample video driver 120, the example application 125, the example S/Wrasterizer 210, the example vertex transformer 212, the example vertexcache 215, the example video driver 220, the example vertex buffer 305,the example redundancy checker 310, the example relative index buffer315, the example walking counter 320, the example relative indexretriever 325, the example vertex buffer indexer 330 and/or the examplegraphics processor invoker 335 could be implemented by one or moreanalog or digital circuit(s), logic circuits, programmable processor(s),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example systems 100 and/or 200, the example vertex buffer fetchers130, 230 and/or 300, the example GPU 105, the example H/W rasterizer110, the example vertex transformer 112, the example vertex cache 115,the example video driver 120, the example application 125, the exampleS/W rasterizer 210, the example vertex transformer 212, the examplevertex cache 215, the example video driver 220, the example vertexbuffer 305, the example redundancy checker 310, the example relativeindex buffer 315, the example walking counter 320, the example relativeindex retriever 325, the example vertex buffer indexer 330 and/or theexample graphics processor invoker 335 is/are hereby expressly definedto include a tangible computer readable storage device or storage disksuch as a memory, a digital versatile disk (DVD), a compact disk (CD), aBlu-ray disk, etc. storing the software and/or firmware. Further still,the example vertex buffer fetchers 130, 230 and/or 300, the examplevertex buffer fetchers 130, 230 and/or 300, the example GPU 105, theexample H/W rasterizer 110, the example vertex transformer 112, theexample vertex cache 115, the example video driver 120, the exampleapplication 125, the example S/W rasterizer 210, the example vertextransformer 212, the example vertex cache 215, the example video driver220, the example vertex buffer 305, the example redundancy checker 310,the example relative index buffer 315, the example walking counter 320,the example relative index retriever 325, the example vertex bufferindexer 330 and/or the example graphics processor invoker 335 of FIGS.1-4 may include one or more elements, processes and/or devices inaddition to, or instead of, those illustrated in FIGS. 1-4, and/or mayinclude more than one of any or all of the illustrated elements,processes and devices.

Flowcharts representative of example machine readable instructions forimplementing the example systems 100 and/or 200, the example vertexbuffer fetchers 130, 230 and/or 300, the example GPU 105, the exampleH/W rasterizer 110, the example vertex transformer 112, the examplevertex cache 115, the example video driver 120, the example application125, the example S/W rasterizer 210, the example vertex transformer 212,the example vertex cache 215, the example video driver 220, the examplevertex buffer 305, the example redundancy checker 310, the examplerelative index buffer 315, the example walking counter 320, the examplerelative index retriever 325, the example vertex buffer indexer 330and/or the example graphics processor invoker 335 are shown in FIGS.5-8. In these examples, the machine readable instructions comprise oneor more programs for execution by a processor, such as the processor 912shown in the example processor platform 900 discussed below inconnection with FIG. 9. The one or more programs, or portion(s) thereof,may be embodied in software stored on a tangible computer readablestorage medium such as a CD-ROM, a floppy disk, a hard drive, a digitalversatile disk (DVD), a Blu-ray Disk™, or a memory associated with theprocessor 912, but the entire program or programs and/or portionsthereof could alternatively be executed by a device other than theprocessor 912 and/or embodied in firmware or dedicated hardware (e.g.,implemented by an ASIC, a PLD, an FPLD, discrete logic, etc.). Also, oneor more of the machine readable instructions represented by theflowcharts of FIGS. 5-8 may be implemented manually. Further, althoughthe example program(s) is(are) described with reference to theflowcharts illustrated in FIGS. 5-8, many other methods of implementingthe example systems 100 and/or 200, the example vertex buffer fetchers130, 230 and/or 300, the example GPU 105, the example H/W rasterizer110, the example vertex transformer 112, the example vertex cache 115,the example video driver 120, the example application 125, the exampleS/W rasterizer 210, the example vertex transformer 212, the examplevertex cache 215, the example video driver 220, the example vertexbuffer 305, the example redundancy checker 310, the example relativeindex buffer 315, the example walking counter 320, the example relativeindex retriever 325, the example vertex buffer indexer 330 and/or theexample graphics processor invoker 335 may alternatively be used. Forexample, with reference to the flowcharts illustrated in FIGS. 5-8, theorder of execution of the blocks may be changed, and/or some of theblocks described may be changed, eliminated, combined and/or subdividedinto multiple blocks.

As mentioned above, the example processes of FIGS. 5-8 may beimplemented using coded instructions (e.g., computer and/or machinereadable instructions) stored on a tangible computer readable storagemedium such as a hard disk drive, a flash memory, a read-only memory(ROM), a compact disk (CD), a digital versatile disk (DVD), a cache, arandom-access memory (RAM) and/or any other storage device or storagedisk in which information is stored for any duration (e.g., for extendedtime periods, permanently, for brief instances, for temporarilybuffering, and/or for caching of the information). As used herein, theterm tangible computer readable storage medium is expressly defined toinclude any type of computer readable storage device and/or storage diskand to exclude propagating signals and to exclude transmission media. Asused herein, “tangible computer readable storage medium” and “tangiblemachine readable storage medium” are used interchangeably. Additionallyor alternatively, the example processes of FIGS. 5-8 may be implementedusing coded instructions (e.g., computer and/or machine readableinstructions) stored on a non-transitory computer and/or machinereadable medium such as a hard disk drive, a flash memory, a ROM, a CD,a DVD, a cache, a RAM and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media. As usedherein, when the phrase “at least” is used as the transition term in apreamble of a claim, it is open-ended in the same manner as the term“comprising” is open ended. Also, as used herein, the terms “computerreadable” and “machine readable” are considered equivalent unlessindicated otherwise.

An example program 500 that may be executed to implement the examplevertex buffer fetcher 300 of FIG. 3 is represented by the flowchartshown in FIG. 5. For convenience, execution of the example program 500is described from the perspective of the vertex buffer fetcher 300 beingused to implement the vertex buffer fetchers 130 and/or 230 of FIGS.1-2. With reference to the preceding figures and associated writtendescriptions, the example program 500 of FIG. 5 begins execution atblock 505 at which the vertex buffer fetcher 300 obtains the inputvertex buffer 305 for rasterization from, for example, the application125, as described above. At block 510, the redundancy checker 310 of thevertex buffer fetcher 300 performs a redundancy checking procedure todetermine the relative index buffer 315 for the input vertex buffer 305obtained at block 505. Example redundancy checking procedures that maybe used to implement the processing at block 510 are described above andin the context of FIG. 6 below.

At block 515, the redundancy checker 310 obtains the relative indexbuffer 315 for the input vertex buffer 305 and associates the relativeindex buffer 315 with the vertex buffer 305 for current and futurerasterization of the vertex buffer 305, as described above. At block520, the vertex buffer fetcher 300 uses the relative index buffer 315associated with the input vertex buffer 305 to perform graphicsprocessing of the vertex buffer 305 (e.g., using the GPU 105 and/or theS/W graphics processor 205) to determine rasterizer outputs associatedwith the entries of the vertex buffer 305. Example graphics processingprocedures based on relative index buffers that may be used to implementthe processing at block 520 are described above and in the context ofFIGS. 7-8 below.

An example program 510P that may be used to implement the processing atblock 510 of FIG. 5 is represented by the flowchart shown in FIG. 6.With reference to the preceding figures and associated writtendescriptions, the example program 510P of FIG. 6 begins execution atblock 605 at which the redundancy checker 310 of the vertex bufferfetcher 300 obtains the size (e.g., 4 bits, 8 bits, 16 bits, etc.) ofthe relative indices stored in the relative index buffer 315. Forexample, the relative index size may correspond to the depth of thevertex cache 115 and/or 215 based on, for example, the relationshipn=log₂ N, where n is the size of the relative indices in bits, and N isthe number of entries in the cache, as described in greater detailabove. At block 610, the redundancy checker 310 initializes a currentiteration index equal to 0. In some examples, the redundancy checker 310can use the walking counter 320 of the vertex buffer fetcher 300 toinitialize and increment the value of the current iteration index in theexample program 510P.

At block 615, the redundancy checker 310 determines whether a currententry of the vertex buffer 305, which corresponds to (e.g., is indexedby) the value of the current iteration index, matches a prior entry ofthe vertex buffer 305 within a prior number of vertex buffer entriesbounded by the relative index size obtained at block 605. For example,the redundancy checker 310 can use a ring buffer, as described above, tofacilitate comparison of current and prior entries of the vertex buffer305. In such examples, the size of the ring, N, which bounds the numberof prior vertex buffer entries to be compared with the current vertexbuffer entry, may be set based on the relative index size, n, to beN=2^(n).

If a match between the current vertex buffer entry and a prior vertexbuffer entry is found (block 620), then at block 625 the redundancychecker 310 sets the relative index buffer entry corresponding to thecurrent vertex buffer entry equal to an offset between the current andmatching prior vertex buffer entries, as described above. However, if amatch between the current vertex buffer entry and a prior vertex bufferentry is not found (block 620), then at block 630 the redundancy checker310 sets the relative index buffer entry corresponding to the currentvertex buffer entry equal to 0, as described above. At block 635, theredundancy checker 310 increments the current iteration index. At block640, the redundancy checker 310 determines whether redundancy checkingof the vertex buffer 305 is complete (e.g., by determining whether thevalue of the current iteration index exceeds the size of the vertexbuffer 305). If redundancy checking of the vertex buffer 305 is notcomplete (block 640), then processing returns to block 615 and theblocks subsequent thereto at which redundancy checking is performed forthe next entry in the vertex buffer 305. Otherwise, execution of theexample program 510P ends.

A first example program 520P1 that may be used to implement theprocessing at block 520 of FIG. 5 is represented by the flowchart shownin FIG. 7. With reference to the preceding figures and associatedwritten descriptions, the example program 520P1 of FIG. 7 beginsexecution at block 705 at which the walking counter 320 of the vertexbuffer fetcher 300 initializes the value of the current iteration indexequal to 0. At block 710, the relative index retriever 325 of the vertexbuffer fetcher 300 retrieves the current relative index, whichcorresponds to the value of the current iteration index, from therelative index buffer 315, as described above. If the value of thecurrent relative index is nonzero (block 715), then at block 720 thevertex buffer indexer 330 of the vertex buffer fetcher 300 determinesthe vertex buffer index for selecting the entry of the vertex buffer 305for rendering to be the value of the current iteration index offset bythe current relative index, as described above. At block 725, thegraphics processor invoker 335 of the vertex buffer fetcher 300 calls,for example, the GPU 105 using the offset vertex buffer index determinedat block 720, which causes the H/W rasterizer 110 included in the GPU105 to fetch and process cached, transformed vertex data associated withthe prior vertex buffer entry pointed to by the offset vertex bufferindex, as described above.

However, if the value of the current relative index is zero (block 715),then at block 730 the vertex buffer indexer 330 determines the vertexbuffer index for selecting the entry of the vertex buffer 305 forrendering to be the value of the current iteration index, as describedabove. At block 735, the graphics processor invoker 335 of the vertexbuffer fetcher 300 calls, for example, the GPU 105 using the non-offsetvertex buffer index determined at block 730, which causes the vertextransformer 112 included in the GPU 105 to fetch and process vertex datafrom the current vertex buffer entry (e.g., because cached vertex datafor the current vertex buffer entry may not be available), which is thenprocessed by the H/W rasterizer 110, as described above. At block 740,the walking counter 320 increments the current iteration index. At block745, relative index retriever 325 determines whether fetching of thevertex buffer 305 for rendering is complete (e.g., by determiningwhether the value of the current iteration index exceeds the size of therelative index buffer 315 and/or the vertex buffer 305). If fetching ofthe vertex buffer 305 is not complete (block 745), then processingreturns to block 710 and the blocks subsequent thereto at which graphicsprocessing based on the next entry of the relative index buffer 315 isperformed. Otherwise, execution of the example program 520P1 ends.

In some examples, the processing at blocks 715, 730 and 735 may beomitted if, for example, the GPU 105 automatically detects vertex cachehits and misses. In such examples, the vertex buffer indexer 330 maycompute the vertex buffer index to be equal to the current iterationindex offset by the current relative index regardless of whether thecurrent relative index is a zero or non-zero value.

A second example program 520P2 that may be used to implement theprocessing at block 520 of FIG. 5 is represented by the flowchart shownin FIG. 8. With reference to the preceding figures and associatedwritten descriptions, the example program 520P2 of FIG. 8 beginsexecution at block 805 at which the walking counter 320 of the vertexbuffer fetcher 300 initializes the value of the current iteration indexequal to 0. At block 810, the relative index retriever 325 of the vertexbuffer fetcher 300 retrieves the current relative index, whichcorresponds to the value of the current iteration index, from therelative index buffer 315, as described above. If the value of thecurrent relative index is nonzero (block 815), then at block 820 thegraphics processor invoker 335 of the vertex buffer fetcher 300determines whether a vertex cache, such as the vertex cache 215, isavailable. If a vertex cache is available (block 820), then at block 825the vertex buffer indexer 330 of the vertex buffer fetcher 300determines the vertex buffer index for selecting the entry of the vertexbuffer 305 for rendering to be the value of the current iteration indexoffset by the current relative index, as described above. At block 825,the graphics processor invoker 335 also uses the offset vertex bufferindex determined by the vertex buffer indexer 330 to access cached,transformed vertex data (e.g., from the vertex cache 215) correspondingto the prior vertex buffer entry indexed by the offset vertex bufferindex, as described above. At block 830, the graphics processor invoker335 invokes, for example, the S/W rasterizer 210 to perform renderingusing the cached vertex data retrieved at block 825, as described above.

However, if a vertex cache is not available (block 820), then at block835 the vertex buffer indexer 330 of the vertex buffer fetcher 300determines the vertex buffer index for selecting the entry of the vertexbuffer 305 for rendering to be the value of the current iteration indexoffset by the current relative index, as described above. At block 825,the graphics processor invoker 335 also uses the offset vertex bufferindex determined by the vertex buffer indexer 330 to fetch vertex datafrom the prior entry of the vertex buffer 305 that is indexed by theoffset vertex buffer index, as described above. At block 840, thegraphics processor invoker 335 invokes, for example, the softwaregraphics processor 205 (e.g., including the vertex transformer 212 andthe S/W rasterizer 210) to perform rendering using the fetched vertexdata retrieved at block 835, as described above.

However, if the value of the current relative index is zero (block 815),then at block 845 the vertex buffer indexer 330 determines the vertexbuffer index for selecting the entry of the vertex buffer 305 forrendering to be the value of the current iteration index, as describedabove. At block 840, the graphics processor invoker 335 invokes, forexample, the software graphics processor 205 (e.g., including the vertextransformer 212 and the S/W rasterizer 210) to perform rendering usingthe fetched vertex data retrieved at block 845, as described above. Atblock 850, the walking counter 320 increments the current iterationindex. At block 855, the relative index retriever 325 determines whetherfetching of the vertex buffer 305 for rendering is complete (e.g., bydetermining whether the value of the current iteration index exceeds thesize of the relative index buffer 315 and/or the vertex buffer 305). Iffetching of the vertex buffer 305 is not complete (block 855), thenprocessing returns to block 810 and the blocks subsequent thereto atwhich rasterization based on the next entry of the relative index buffer315 is performed. Otherwise, execution of the example program 520P2ends.

Tables 1 and 2 illustrate respective pseudocode for implementing a priorrasterization technique and a disclosed example rasterization technique.In particular, Table 1 illustrates a prior rasterization technique basedon absolute indexing of a vertex buffer. At line 1 of Table 1, a currentiteration index (currentIndex) is initialized to 0. At line 2 of Table1, the pseudocode iterates through an absolute index buffer(AbsIndexBuffer). For a given iteration, at line 3 of Table 1, thevertex buffer index (vbIndex) for vertex buffer entry to be rendered isset to the value of the absolute index buffer (AbsIndexBuffer) entryindexed by the current iteration index (currentIndex). At line 4 ofTable 1, the vertex data (vertex) to be rendered for the currentiteration is retrieved from the vertex buffer (VertexBuffer) using thevertex buffer index (vbIndex), which was set to be equal to the absoluteindex value retrieved from the absolute index buffer (AbsIndexBuffer).At line 5 of Table 1, processing of the vertex data (vertex) isperformed by calling a RunVertexTransformer function. At line 6 of Table1, the current iteration index (currentIndex) is incremented by 1.

TABLE 1 1: currentIndex <- 0 2: while currentIndex <length(AbsIndexBuffer): 3:  vbIndex <- AbsIndexBuffer(currentIndex)4:  vertex <- GetVertex(vbIndex, VertexBuffer) 5:  RunVertexTransformer(vertex) 6:  currentIndex <- currentIndex + 1

Table 2 illustrates example rasterization technique based on relativeindexing of the vertex buffer in accordance with the examples disclosedherein. At line 11 of Table 2, a current iteration index (currentIndex)is initialized to 0. At line 12 of Table 2, the pseudocode iteratesthrough a relative index buffer (RelativeIndexBuffer). For a giveniteration, at line 13 of Table 2, the current relative index (relIndex)corresponding to the current vertex buffer entry to be rendered isretrieved from the relative index buffer (RelativeIndexBuffer). At line14 of Table 2, the vertex buffer index (vbIndex) for vertex buffer entryto be rendered is set to the value of the current iteration index(currentIndex) offset by the current relative index (relIndex). At line15 of Table 2, the vertex data (vertex) to be rendered for the currentiteration is retrieved from the vertex buffer (VertexBuffer) using thevertex buffer index (vbIndex), which was set to be equal to the currentiteration index (currentIndex) offset by the current relative index(relIndex). At line 16 of Table 2, processing of the vertex data(vertex) is performed by calling a RunVertexTransformer function. Atline 7 of Table 2, the current iteration index (currentIndex) isincremented by 1.

TABLE 2 11: currentIndex <- 0 12: while currentIndex<length(RelativeIndexBuffer): 13:  relIndex <-RelativeIndexBuffer(currentIndex) 14:  vbIndex <- currentIndex -relIndex 15:  vertex <- GetVertex(vbIndex, VertexBuffer)16:  RunVertexTransformer (vertex) 17:  currentIndex <- currentIndex + 1

FIG. 9 is a block diagram of an example processor platform 900 capableof executing the instructions of FIGS. 5-8 to implement the examplesystems 100 and/or 200, the example vertex buffer fetchers 130, 230and/or 300, the example GPU 105, the example H/W rasterizer 110, theexample vertex transformer 112, the example vertex cache 115, theexample video driver 120, the example application 125, the example S/Wrasterizer 210, the example vertex transformer 212, the example vertexcache 215, the example video driver 220, the example vertex buffer 305,the example redundancy checker 310, the example relative index buffer315, the example walking counter 320, the example relative indexretriever 325, the example vertex buffer indexer 330 and/or the examplegraphics processor invoker 335 of FIGS. 1-4. The processor platform 900can be, for example, a server, a personal computer, a mobile device(e.g., a cell phone, a smart phone, a tablet such as an iPad™), apersonal digital assistant (PDA), an Internet appliance, a DVD player, aCD player, a digital video recorder, a Blu-ray player, a gaming console,a personal video recorder, a set top box, a digital camera, or any othertype of computing device.

The processor platform 900 of the illustrated example includes aprocessor 912. The processor 912 of the illustrated example is hardware.For example, the processor 912 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors or controllers fromany desired family or manufacturer.

The processor 912 of the illustrated example includes a local memory 913(e.g., a cache) (e.g., a cache). The processor 912 of the illustratedexample is in communication with a main memory including a volatilememory 914 and a non-volatile memory 916 via a link 918. The link 918may be implemented by a bus, one or more point-to-point connections,etc., or a combination thereof. The volatile memory 914 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM)and/or any other type of random access memory device. The non-volatilememory 916 may be implemented by flash memory and/or any other desiredtype of memory device. Access to the main memory 914, 916 is controlledby a memory controller.

The processor platform 900 of the illustrated example also includes aninterface circuit 920. The interface circuit 920 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), and/or a PCI express interface.

In the illustrated example, one or more input devices 922 are connectedto the interface circuit 920. The input device(s) 922 permit(s) a userto enter data and commands into the processor 912. The input device(s)can be implemented by, for example, an audio sensor, a microphone, acamera (still or video), a keyboard, a button, a mouse, a touchscreen, atrack-pad, a trackball, a trackbar (such as an isopoint), a voicerecognition system and/or any other human-machine interface. Also, manysystems, such as the processor platform 900, can allow the user tocontrol the computer system and provide data to the computer usingphysical gestures, such as, but not limited to, hand or body movements,facial expressions, and face recognition.

One or more output devices 924 are also connected to the interfacecircuit 920 of the illustrated example. The output devices 924 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay, a cathode ray tube display (CRT), a touchscreen, a tactileoutput device, a light emitting diode (LED), a printer and/or speakers).The interface circuit 920 of the illustrated example, thus, typicallyincludes a graphics driver card, a graphics driver chip or a graphicsdriver processor.

The interface circuit 920 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem and/or network interface card to facilitate exchange of data withexternal machines (e.g., computing devices of any kind) via a network926 (e.g., an Ethernet connection, a digital subscriber line (DSL), atelephone line, coaxial cable, a cellular telephone system, etc.).

The processor platform 900 of the illustrated example also includes oneor more mass storage devices 928 for storing software and/or data.Examples of such mass storage devices 928 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, RAID(redundant array of independent disks) systems, and digital versatiledisk (DVD) drives.

Coded instructions 932 corresponding to the instructions of FIGS. 5-8may be stored in the mass storage device 928, in the volatile memory914, in the non-volatile memory 916, in the local memory 913 and/or on aremovable tangible computer readable storage medium, such as a CD or DVD936.

The following further examples include subject matter such as a method,means for performing acts of the method, at least one machine-readablemedium including instructions that, when performed by a machine causethe machine to performs acts of the method, an apparatus and/or systemfor graphics processing of a vertex buffer using a relative index bufferaccording to embodiments and examples disclosed herein.

Example 1 is a method to process a vertex buffer, the method includingaccessing a first relative index stored in a relative index buffer, thefirst relative index specifying an offset from a current index selectinga first entry of the vertex buffer. The method of example 1 alsoincludes, in response to the first relative index being a nonzero value,processing data associated with a second entry of the vertex buffer todetermine a rasterizer output associated with the first entry of thevertex buffer, the second entry of the vertex buffer being selectedusing the current index offset by the first relative index.

Example 2 may include the subject matter of example 1, and may furtherinclude, in response to the first relative index being zero, fetchingand processing the first entry of the vertex buffer to determine therasterizer output associated with the first entry of the vertex buffer.

Example 3 may include the subject matter of examples 1 and/or 2, whereinthe first relative index is associated with the first entry of thevertex buffer, and the first relative index is selected from therelative index buffer using the current index.

Example 4 may include the subject matter of one or more of examples 1 to3, wherein the relative index buffer stores relative indexes associatedwith respective entries of the vertex buffer, the relative index bufferis accessed iteratively using the current index, and the current indexis incremented at each iteration of accessing the relative index buffer.

Example 5 may include the subject matter of one or more of examples 1 to4, wherein the data associated with the second entry of the vertexbuffer is cached data associated with the second entry of the vertexbuffer, and processing the data associated with the second entry of thevertex buffer includes (1) calculating an index value corresponding tothe current index offset by the first relative index, and (2) calling arasterizer using the index value to cause the rasterizer to access thecached data associated with the second entry of the vertex buffer.

Example 6 may include the subject matter of one or more of examples 1 to4, wherein processing the data associated with the second entry of thevertex buffer includes (1) when a vertex cache is present, accessingfirst data from the vertex cache, the first data obtained from previousrasterization processing associated with the second entry of the vertexbuffer, and (2) when the vertex cache is not present, fetching seconddata included in the second entry of the vertex buffer and performingrasterization using the fetched second data.

Example 7 may include the subject matter of examples 1 to 6, and mayfurther include (1) comparing entries of the vertex buffer with pastentries of the vertex buffer within a prior number of vertex bufferentries, the prior number of entries being based on a relative indexsize, and (2) in response to determining that the first entry of thevertex buffer matches the second entry of the vertex buffer, setting thefirst relative index equal to an offset between the first entry of thevertex buffer and the second entry of the vertex buffer.

Example 8 is a computer readable storage medium including computerreadable instructions which, when executed, may cause a computer toperform the method defined in any one or more of claims 1 to 7.

Example 9 is a tangible machine readable storage medium includingmachine readable instructions which, when executed, cause a machine toat least access a first relative index stored in a relative indexbuffer, the first relative index specifying an offset from a currentindex selecting a first entry of a vertex buffer. The instructions ofexample 9, when executed, also cause the machine to at least, inresponse to the first relative index being a nonzero value, process dataassociated with a second entry of the vertex buffer to determine arasterizer output associated with the first entry of the vertex buffer,the second entry of the vertex buffer being selected using the currentindex offset by the first relative index.

Example 10 may include the subject matter of example 9, wherein themachine readable instructions, when executed, may further cause themachine to, in response to the first relative index being zero, fetchand process the first entry of the vertex buffer to determine therasterizer output associated with the first entry of the vertex buffer.

Example 11 may include the subject matter of examples 9 and/or 10,wherein the first relative index is associated with the first entry ofthe vertex buffer, and the first relative index is selected from therelative index buffer using the current index.

Example 12 may include the subject matter of one or more of examples 9to 11, wherein the relative index buffer stores relative indexesassociated with respective entries of the vertex buffer, the relativeindex buffer is accessed iteratively using the current index, and thecurrent index is incremented at each iteration of accessing the relativeindex buffer.

Example 13 may include the subject matter of one or more of examples 9to 12, wherein the data associated with the second entry of the vertexbuffer is cached data associated with the second entry of the vertexbuffer, and the machine readable instructions, when executed, mayfurther cause the machine to (1) calculate an index value correspondingto the current index offset by the first relative index, and (2) call arasterizer using the index value to cause the rasterizer to access thecached data associated with the second entry of the vertex buffer.

Example 14 may include the subject matter of one or more of examples 9to 12, wherein the machine readable instructions, when executed, furthercause the machine to (1) when a vertex cache is present, access firstdata from the vertex cache, the first data obtained from previousrasterization processing associated with the second entry of the vertexbuffer, and (2) when the vertex cache is not present, fetch second dataincluded in the second entry of the vertex buffer and performrasterization using the fetched second data.

Example 15 may include the subject matter of one or more of examples 9to 14, wherein the machine readable instructions, when executed, mayfurther cause the machine to (1) compare entries of the vertex bufferwith past entries of the vertex buffer within a prior number of vertexbuffer entries, the prior number of entries being based on a relativeindex size, and (2) in response to the first entry of the vertex bufferbeing determined to match the second entry of the vertex buffer, set thefirst relative index equal to an offset between the first entry of thevertex buffer and the second entry of the vertex buffer.

Example 16 is an apparatus to rasterize a vertex buffer using a relativeindex buffer, the apparatus including an index retriever to access afirst relative index stored in the relative index buffer, the firstrelative index specifying an offset from a current index selecting afirst entry of the vertex buffer. The apparatus of example 16 alsoincludes an invoker to cause a rasterizer to process data associatedwith a second entry of the vertex buffer to determine a rasterizeroutput associated with the first entry of the vertex buffer in responseto the first relative index being a nonzero value, the second entry ofthe vertex buffer being selected using the current index offset by thefirst relative index.

Example 17 may include the subject matter of example 16, wherein, inresponse to the first relative index being zero, the invoker is to causethe rasterizer to process data associated with the first entry of thevertex buffer to determine the rasterizer output associated with thefirst entry of the vertex buffer.

Example 18 may include the subject matter of examples 16 and/or 17,wherein the first relative index is associated with the first entry ofthe vertex buffer, and the first relative index is selected from therelative index buffer using the current index.

Example 19 may include the subject matter of one or more of examples 16to 18, wherein the relative index buffer stores relative indexesassociated with respective entries of the vertex buffer, the indexretriever is to access the relative index buffer iteratively using thecurrent index, and may further include a counter to increment thecurrent index at each iteration of accessing the relative index buffer.

Example 20 may include the subject matter of one or more of examples 16to 19, wherein the data associated with the second entry of the vertexbuffer is cached data associated with the second entry of the vertexbuffer, the apparatus may further include a buffer indexer to calculatean index value corresponding to the current index offset by the firstrelative index, and the invoker to call the rasterizer using the indexvalue to cause the rasterizer to access the cached data associated withthe second entry of the vertex buffer.

Example 21 may include the subject matter of one or more of examples 16to 19, wherein the invoker is further to (1) when a vertex cache ispresent, access first data from the vertex cache, the first dataobtained from previous rasterization processing of the second entry ofthe vertex buffer, and (2) when the vertex cache is not present, fetchsecond data included in the second entry of the vertex buffer and causethe rasterizer to perform rasterization using the fetched second data.

Example 22 may include the subject matter of one or more of examples 16to 21, and may further include a redundancy checker to (1) compareentries of the vertex buffer with past entries of the vertex bufferwithin a prior number of vertex buffer entries, the prior number ofentries being based on a relative index size, and (2) in response to thefirst entry of the vertex buffer being determined to match the secondentry of the vertex buffer, set the first relative index equal to anoffset between the first entry of the vertex buffer and the second entryof the vertex buffer.

Example 23 is an apparatus to rasterize a vertex buffer using a relativeindex buffer, the apparatus including means for accessing a firstrelative index stored in a relative index buffer, the first relativeindex specifying an offset from a current index selecting a first entryof the vertex buffer. The apparatus of example 33 also includes meansfor processing data associated with a second entry of the vertex buffer,in response to the first relative index being a nonzero value, todetermine a rasterizer output associated with the first entry of thevertex buffer, the second entry of the vertex buffer being selectedusing the current index offset by the first relative index.

Example 24 may include the subject matter of example 23, and may furtherinclude means for fetching and processing the first entry of the vertexbuffer, in response to the first relative index being zero, to determinethe rasterizer output associated with the first entry of the vertexbuffer.

Example 25 may include the subject matter of examples 23 and/or 24,wherein the first relative index is associated with the first entry ofthe vertex buffer, and the first relative index is selected from therelative index buffer using the current index.

Example 26 may include the subject matter of one or more of examples 23to 25, wherein the relative index buffer stores relative indexesassociated with respective entries of the vertex buffer, the relativeindex buffer is accessed iteratively using the current index, and thecurrent index is incremented at each iteration of accessing the relativeindex buffer.

Example 27 may include the subject matter of one or more of examples 23to 26, wherein the data associated with the second entry of the vertexbuffer is cached data associated with the second entry of the vertexbuffer, and the means for processing the data associated with the secondentry of the vertex buffer includes (1) means for calculating an indexvalue corresponding to the current index offset by the first relativeindex, and (2) means for calling a rasterizer using the index value tocause the rasterizer to access the cached data associated with thesecond entry of the vertex buffer.

Example 28 may include the subject matter of one or more of examples 23to 26, wherein processing the data associated with the second entry ofthe vertex buffer includes (1) means for accessing first data from avertex cache when the vertex cache is present, the first data obtainedfrom previous rasterization processing associated with the second entryof the vertex buffer, and (2) means for fetching second data included inthe second entry of the vertex buffer and performing rasterization usingthe fetched second data when the vertex cache is not present.

Example 29 may include the subject matter of one or more of examples 23to 28, and may further include (1) means for comparing entries of thevertex buffer with past entries of the vertex buffer within a priornumber of vertex buffer entries, the prior number of entries being basedon a relative index size, and (2) means for setting the first relativeindex equal to an offset between the first entry of the vertex bufferand the second entry of the vertex buffer in response to determiningthat the first entry of the vertex buffer matches the second entry ofthe vertex buffer.

Example 30 is an apparatus (300) to rasterize a vertex buffer (305)using a relative index buffer (315), the apparatus (300) including anindex retriever (325) to access a first relative index stored in therelative index buffer (315), the first relative index specifying anoffset from a current index selecting a first entry of the vertex buffer(305). The apparatus (300) of example 43 also includes an invoker (335)to cause a rasterizer (110, 210) to process data associated with asecond entry of the vertex buffer (305) to determine a rasterizer outputassociated with the first entry of the vertex buffer (305) in responseto the first relative index being a nonzero value, the second entry ofthe vertex buffer (305) being selected using the current index offset bythe first relative index.

Example 31 may include the subject matter of example 30, wherein, inresponse to the first relative index being zero, the invoker (335) is tocause the rasterizer (110, 210) to process data associated with thefirst entry of the vertex buffer (305) to determine the rasterizeroutput associated with the first entry of the vertex buffer (305).

Example 32 may include the subject matter of examples 30 and/or 31,wherein the first relative index is associated with the first entry ofthe vertex buffer (305), and the first relative index is selected fromthe relative index buffer (315) using the current index.

Example 33 may include the subject matter of example 32, wherein therelative index buffer (315) stores relative indexes associated withrespective entries of the vertex buffer (305), the index retriever (325)is to access the relative index buffer (315) iteratively using thecurrent index, and further including a counter (320) to increment thecurrent index at each iteration of accessing the relative index buffer(315).

Example 34 may include the subject matter of one or more of examples 30to 33, wherein the data associated with the second entry of the vertexbuffer (305) is cached data associated with the second entry of thevertex buffer (305), the apparatus (305) further includes a bufferindexer (330) to calculate an index value corresponding to the currentindex offset by the first relative index, and the invoker (335) is tocall the rasterizer (110) using the index value to cause the rasterizer(110) to access the cached data associated with the second entry of thevertex buffer.

Example 35 may include the subject matter of one or more of examples 30to 33, wherein the invoker (335) is further to 91) when a vertex cache(215) is present, access first data from the vertex cache (215), thefirst data obtained from previous rasterization processing of the secondentry of the vertex buffer (305), and (2) when the vertex cache (215) isnot present, fetch second data included in the second entry of thevertex buffer (305) and cause the rasterizer (210) to performrasterization using the fetched second data.

Example 36 may include the subject matter of one or more of examples 30to 35, and may further include a redundancy checker (310) to (1) compareentries of the vertex buffer (305) with past entries of the vertexbuffer (305) within a prior number of vertex buffer entries, the priornumber of entries being based on a relative index size, and (2) inresponse to the first entry of the vertex buffer (305) being determinedto match the second entry of the vertex buffer (305), set the firstrelative index equal to an offset between the first entry of the vertexbuffer (305) and the second entry of the vertex buffer (305).

Example 37 is a method to process a vertex buffer (305), the methodincluding accessing a first relative index stored in a relative indexbuffer (315), the first relative index specifying an offset from acurrent index selecting a first entry of the vertex buffer (305). Themethod of example 50 also includes, in response to the first relativeindex being a nonzero value, processing data associated with a secondentry of the vertex buffer (305) to determine a rasterizer outputassociated with the first entry of the vertex buffer (305), the secondentry of the vertex buffer (305) being selected using the current indexoffset by the first relative index.

Example 38 may include the subject matter of example 37, and may furtherinclude, in response to the first relative index being zero, fetchingand processing the first entry of the vertex buffer (305) to determinethe rasterizer output associated with the first entry of the vertexbuffer (305).

Example 39 may include the subject matter of examples 37 and/or 38,wherein the first relative index is associated with the first entry ofthe vertex buffer (305), and the first relative index is selected fromthe relative index buffer (315) using the current index.

Example 40 may include the subject matter of example 39, wherein therelative index buffer (315) stores relative indexes associated withrespective entries of the vertex buffer (305), the relative index buffer(315) is accessed iteratively using the current index, and the currentindex is incremented at each iteration of accessing the relative indexbuffer (305).

Example 41 may include the subject matter of one or more of examples 37to 40, wherein the data associated with the second entry of the vertexbuffer (305) is cached data associated with the second entry of thevertex buffer (305), and processing the data associated with the secondentry of the vertex buffer (305) includes (1) calculating an index valuecorresponding to the current index offset by the first relative index,and (2) calling a rasterizer (110) using the index value to cause therasterizer (110) to access the cached data associated with the secondentry of the vertex buffer (305).

Example 42 may include the subject matter of one or more of examples 37to 40, wherein processing the data associated with the second entry ofthe vertex buffer (305) includes (1) when a vertex cache (215) ispresent, accessing first data from the vertex cache (215), the firstdata obtained from previous rasterization processing associated with thesecond entry of the vertex buffer (305), and (2) when the vertex cache(215) is not present, fetching second data included in the second entryof the vertex buffer (305) and performing rasterization using thefetched second data.

Example 43 may include the subject matter of one or more of examples 37to 42, and may further include (1) comparing entries of the vertexbuffer (305) with past entries of the vertex buffer (305) within a priornumber of vertex buffer entries, the prior number of entries being basedon a relative index size, and (2) in response to determining that thefirst entry of the vertex buffer (305) matches the second entry of thevertex buffer (305), setting the first relative index equal to an offsetbetween the first entry of the vertex buffer (305) and the second entryof the vertex buffer (305).

Example 44 is a computer readable storage medium including computerreadable instructions which, when executed, may cause a computer toperform the method defined in any one or more of examples 37 to 43.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. A method to process a vertex buffer, the methodcomprising: accessing a first relative index stored in a relative indexbuffer, the first relative index associated with a first entry of thevertex buffer corresponding to a current index, the first relative indexspecifying an offset to be at least one of added to or subtracted fromthe current index corresponding to the first entry of the vertex buffer;and in response to the first relative index being a nonzero value,processing data associated with a second entry of the vertex bufferdifferent from the first entry of the vertex buffer to determine arasterizer output associated with the first entry of the vertex buffer,the second entry of the vertex buffer being selected using an indexvalue based on the offset specified by the first relative index being atleast one of added to or subtracted from the current index.
 2. A methodas defined in claim 1, further including, in response to the firstrelative index being zero, fetching and processing the first entry ofthe vertex buffer to determine the rasterizer output associated with thefirst entry of the vertex buffer.
 3. A method as defined in claim 1,wherein the first relative index is selected from the relative indexbuffer using the current index.
 4. A method as defined in claim 3,wherein the relative index buffer stores relative indexes associatedwith respective entries of the vertex buffer, the relative index bufferis accessed iteratively using the current index, and the current indexis incremented at each iteration of accessing the relative index buffer.5. A method as defined in claim 1, wherein the data associated with thesecond entry of the vertex buffer is cached data, and the processing ofthe data associated with the second entry of the vertex buffer includes:calling a rasterizer using the index value to cause the rasterizer toaccess the cached data associated with the second entry of the vertexbuffer.
 6. A method as defined in claim 1, wherein the processing of thedata associated with the second entry of the vertex buffer includes:when a vertex cache is present, accessing first data from the vertexcache, the first data obtained from previous rasterization processingassociated with the second entry of the vertex buffer; and when thevertex cache is not present: fetching second data included in the secondentry of the vertex buffer; and performing rasterization using thefetched second data.
 7. A method as defined in claim 1, furtherincluding: comparing entries of the vertex buffer with past entries ofthe vertex buffer within a prior number of vertex buffer entries, theprior number of entries being based on a relative index size; and inresponse to determining that the first entry of the vertex buffermatches the second entry of the vertex buffer, setting the firstrelative index equal to an offset between the first entry of the vertexbuffer and the second entry of the vertex buffer.
 8. At least onenon-transitory computer readable storage medium comprising machinereadable instructions which, when executed, cause a machine to at least:access a first relative index stored in a relative index buffer, thefirst relative index associated with a first entry of a vertex buffercorresponding to a current index, the first relative index specifying anoffset to be at least one of added to or subtracted from the currentindex corresponding to the first entry of the vertex buffer; and inresponse to the first relative index being a nonzero value, process dataassociated with a second entry of the vertex buffer different from thefirst entry of the vertex buffer to determine a rasterizer outputassociated with the first entry of the vertex buffer, the second entryof the vertex buffer being selected using an index value equal to theoffset specified by the first relative index at least one of added to orsubtracted from the current index.
 9. At least one storage medium asdefined in claim 8, wherein the machine readable instructions, whenexecuted, further cause the machine to, in response to the firstrelative index being zero, fetch and process the first entry of thevertex buffer to determine the rasterizer output associated with thefirst entry of the vertex buffer.
 10. At least one storage medium asdefined in claim 8, wherein the first relative index is selected fromthe relative index buffer using the current index.
 11. At least onestorage medium as defined in claim 10, wherein the relative index bufferstores relative indexes associated with respective entries of the vertexbuffer, the relative index buffer is accessed iteratively using thecurrent index, and the current index is incremented at each iteration ofaccessing the relative index buffer.
 12. At least one storage medium asdefined in claim 8, wherein the data associated with the second entry ofthe vertex buffer is cached data, and to process the data associatedwith the second entry of the vertex buffer, the machine readableinstructions, when executed, cause the machine to: call a rasterizerusing the index value to cause the rasterizer to access the cached dataassociated with the second entry of the vertex buffer.
 13. At least onestorage medium as defined in claim 8, wherein to process the dataassociated with the second entry of the vertex buffer, the machinereadable instructions, when executed, cause the machine to: when avertex cache is present, access first data from the vertex cache, thefirst data obtained from previous rasterization processing associatedwith the second entry of the vertex buffer; and when the vertex cache isnot present: fetch second data included in the second entry of thevertex buffer; and perform rasterization using the fetched second data.14. At least one storage medium as defined in claim 8, wherein themachine readable instructions, when executed, further cause the machineto: compare entries of the vertex buffer with past entries of the vertexbuffer within a prior number of vertex buffer entries, the prior numberof entries being based on a relative index size; and in response to thefirst entry of the vertex buffer being determined to match the secondentry of the vertex buffer, set the first relative index equal to anoffset between the first entry of the vertex buffer and the second entryof the vertex buffer.
 15. An apparatus to rasterize a vertex bufferusing a relative index buffer, the apparatus comprising: an indexretriever to access a first relative index stored in the relative indexbuffer, the first relative index associated with a first entry of thevertex buffer corresponding to a current index, the first relative indexspecifying an offset to be at least one of added to or subtracted fromthe current index corresponding to the first entry of the vertex buffer;and an invoker to cause a rasterizer to process data associated with asecond entry of the vertex buffer different from the first entry of thevertex buffer to determine a rasterizer output associated with the firstentry of the vertex buffer in response to the first relative index beinga nonzero value, the second entry of the vertex buffer being selectedusing an index value determined by at least one of adding the offsetspecified by the first relative index to the current index orsubtracting the offset specified by the first relative index from thecurrent index.
 16. An apparatus as defined in claim 15, wherein, inresponse to the first relative index being zero, the invoker is to causethe rasterizer to process data associated with the first entry of thevertex buffer to determine the rasterizer output associated with thefirst entry of the vertex buffer.
 17. An apparatus as defined in claim15, wherein the relative index buffer stores relative indexes associatedwith respective entries of the vertex buffer, the index retriever is toaccess the relative index buffer iteratively using the current index,and further including a counter to increment the current index at eachiteration of accessing the relative index buffer.
 18. An apparatus asdefined in claim 15, wherein the data associated with the second entryof the vertex buffer is cached data, and the invoker is to call therasterizer using the index value to cause the rasterizer to access thecached data associated with the second entry of the vertex buffer. 19.An apparatus as defined in claim 15, wherein the invoker is further to:when a vertex cache is present, access first data from the vertex cache,the first data obtained from previous rasterization processing of thesecond entry of the vertex buffer; and when the vertex cache is notpresent: fetch second data included in the second entry of the vertexbuffer; and cause the rasterizer to perform rasterization using thefetched second data.
 20. An apparatus as defined in claim 15, furtherincluding a redundancy checker to: compare entries of the vertex bufferwith past entries of the vertex buffer within a prior number of vertexbuffer entries, the prior number of entries being based on a relativeindex size; and in response to the first entry of the vertex bufferbeing determined to match the second entry of the vertex buffer, set thefirst relative index equal to an offset between the first entry of thevertex buffer and the second entry of the vertex buffer.
 21. Anapparatus as defined in claim 15, further including a display device todisplay the rasterizer output.